Self-lubricating ceramic downhole bearings

ABSTRACT

A multiphase pumping system comprising an electric submersible pumping system. To accommodate the multiphase environment, the electric submersible pumping system utilizes self-lubricating, abrasion resistant ceramic bearings. In one embodiment, the bearings are made from graphite impregnated silicon carbide.

FIELD OF THE INVENTION

[0001] The present invention relates generally to the production of hydrocarbon-based fluids from subterranean locations. More specifically, the present invention relates to downhole bearings adapted for use in environments having poor or inadequate lubrication.

BACKGROUND OF THE INVENTION

[0002] The production of fluids from subterranean reservoirs is accomplished by a variety of methods. For example, oil is commonly produced to the surface of the earth by drilling a wellbore into a formation containing the desired fluid. Subsequently, an artificial lift mechanism is deployed within the wellbore, and oil is produced to the surface of the earth or to another storage location.

[0003] Artificial lift is commonly provided by pumping systems, such as electric submersible pumping systems. When using such systems, a submersible pump powered by a submersible motor is moved into the wellbore until at least partially submersed in the fluid that has flowed into the wellbore from the surrounding formation. The pump is then powered to move the fluid, e.g. oil, from the wellbore to a desired location.

[0004] In a typical wellbore environment, the components of the pumping system are immersed in fluid and thus maintain adequate lubrication. However, the fluid can contain particulates, such as sand, that can be detrimental to the operation of the system components, such as bearings. Thus, the bearings in such wellbore environments need to provide sufficient abrasion resistance.

[0005] In multiphase wellbore environments, the bearings of the multiphase pumping system are subjected to fluids having high gas volume. In such environments, the bearings of the pumping system must not only be resistant to the particulates contained within the fluid, but must also be robust enough to survive periods of poor or inadequate lubrication.

[0006] There exists, therefore, a need for downhole bearings particularly suited for operation in downhole environments that provide poor or inadequate lubrication, such as multiphase environments.

SUMMARY OF THE INVENTION

[0007] The present invention provides a multiphase pumping system comprising an electric submersible pumping system having self-lubricating, abrasion resistant ceramic bearings. In an embodiment of the present invention, the bearings are made from graphite impregnated silicon carbide.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and:

[0009]FIG. 1 is a front elevational view of an exemplary fluid production device incorporating a lubrication system, according to one embodiment of the present invention;

[0010]FIG. 2 is a cross-sectional view of a portion of an exemplary multiphase submersible pump taken generally along its axis.

[0011]FIG. 3 is a schematic of an exemplary multiphase motor protector taken generally along its axis.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0012] Referring generally to FIG. 1, an artificial lift mechanism 10 is illustrated at a subterranean location 12. In this specific embodiment, the artificial lift mechanism 10 comprises an electric submersible pumping system. However, it should be noted that a variety of artificial lift mechanisms 10 can be utilized, and the number, type and arrangement of components within a given artificial lift mechanism 10 may vary substantially. For purposes of explanation, the artificial lift mechanism 10 will be described as an electric submersible pumping system having the exemplary components illustrated in FIG. 1 and described below.

[0013] As illustrated in FIG. 1, the electric submersible pumping system 10 is deployed in a wellbore environment in which a wellbore 14 is drilled into a subterranean formation 16 containing a hydrocarbon-based fluid, such as oil 18. In the example illustrated, wellbore 14 is lined with a wellbore casing 20 having a plurality of openings 22, sometimes referred to as perforations, through which oil 18 flows from the formation 16 into the wellbore 14. The wellbore casing 20 extends upwardly through the wellbore 14 to a wellhead 24 that may be disposed, for example, at a surface 26 of the earth.

[0014] The exemplary electric submersible pumping system 10 comprises a submersible motor 28 powered by an electrical power cable 30. The electric submersible pumping system 10 further comprises a motor protector 32 and a submersible pump 34 having a pump intake 36. In this example, the submersible pump 34 comprises a centrifugal style pump. Furthermore, the submersible pump 34, the motor protector 32 and the submersible motor 28 are illustrated as coupled to each other for purposes of explanation only. Additional motors, pumps or other components can be inserted or exchanged for a given application.

[0015] When using downhole pumping systems 10 in multiphase environments, the pumping systems 10 are being used to produce fluids having a high percentage of gas by volume. In such instances, the bearings of the motor protector 32 and the submersible pump 34 are not operating in an all liquid environment and must be able to survive periods of poor or inadequate lubrication. At the same time, the bearings of the motor protector 32 and the submersible pump 34 must still be resistant to the abrasive particulates, such as sand, carried by the fluid.

[0016] For operation in downhole multiphase environments, the present invention provides a self-lubricating, abrasion resistant ceramic bearing adapted for use with multiphase pumping systems. In one embodiment, the bearings of the present invention are made from a graphite impregnated silicon carbide material. The graphite impregnated silicon carbide bearing provides dry running capability as well as abrasion resistance.

[0017]FIG. 2 illustrates an embodiment of the present invention, wherein the self-lubricating, abrasion resistant ceramic bearings are used in a submersible pump 34 of a multiphase pumping system 10. As shown, the submersible pump 34 is a multi-stage, multiphase pump. A plurality of pump stages are provided between the pump intake 36 and the pump discharge 40. The number of stages is dependent upon the desired amount of energy to be imparted to the fluid.

[0018] Each pump stage comprises an impeller 42 and a diffuser 44. The impellers 42 are affixed to the pump shaft 46 and rotate to increase the energy of the fluid traveling therethrough. The diffusers 44 are affixed to the pump housing 48 and are located at the outlet of each impeller 42.

[0019] To accommodate the rotation of the pump shaft 46, self-lubricating, abrasion resistant ceramic bearings 50 of the present invention are provided intermediate the pump shaft 46 and the diffusers 44. As discussed above, the ceramic bearings 50 of the present invention provide dry running capability as well as abrasion resistance particularly suitable for a downhole multiphase environment.

[0020] In the illustration shown, the self-lubricating, abrasion resistant ceramic bearings 50 are radial journal bearings having a bushing 52 affixed to the diffuser 44 and a sleeve 54 affixed to the pump shaft 46. It should be understood, however, that the bearings 50 of the present invention can comprise any number of other types of bearings. For example, the self-lubricating, abrasion resistant ceramic bearings 50 can be thrust bearings, tilt pad bearings, lobed bearings, lemon bore bearings, pressure dam bearings, or the like.

[0021]FIG. 3 illustrates an embodiment of the present invention, wherein the self-lubricating, abrasion resistant ceramic bearings are used in a motor protector 32 of a multiphase pumping system 10. The exemplary multiphase pumping system 10 comprises a submersible pump 34, a submersible motor 28 and various motor protection components disposed in a housing 52. The submersible pump 34 is rotatably coupled to the submersible motor 28 via a shaft 46 that extends lengthwise through the housing 52 (e.g., one or more housing sections coupled together).

[0022] The motor protector 32 provides shaft seals 54, 56, a pressure compensation assembly 58, and various other components designed to isolate the submersible motor 28 while permitting the expansion and contraction of the internal motor fluid. A thrust bearing 60 is disposed about the pump shaft 46 to accommodate and support the thrust load from the submersible pump 34.

[0023] In the embodiment of the present invention shown in FIG. 3, the thrust bearing 60 is a self-lubricating, abrasion resistant ceramic bearing. As such, the thrust bearing 60 provides dry running capability as well as abrasion resistance and is particularly suited for use in a downhole multiphase environment.

[0024] It should be understood that the foregoing description is of exemplary embodiments of this invention, and that the invention is not limited to the specific forms shown. For example, a variety of pumping systems can benefit from the type of self-lubricating, abrasion resistant ceramic bearings discussed herein. A wide variety of pump components, currently available or potentially developed in the future, may benefit from the bearings of the present invention. These and other modifications may be made in the implementation of the bearings without departing from the scope of the invention as expressed in the appended claims. 

What is claimed is:
 1. A multiphase pumping system, comprising: a rotary pumping system having self-lubricating, abrasion resistant ceramic bearings.
 2. The multiphase pumping system of claim 1, wherein the self-lubricating, abrasion resistant ceramic bearings comprise graphite impregnated silicon carbide.
 3. The multiphase pumping system of claim 1, wherein the self-lubricating, abrasion resistant ceramic bearings are radial journal bearings.
 4. The multiphase pumping system of claim 1, wherein the self-lubricating, abrasion resistant ceramic bearings are selected from thrust bearings, tilt pad bearings, lobed bearings, lemon bore bearings, and pressure dam bearings.
 5. A self-lubricating, abrasion resistant bearing adapted for downhole multiphase pumping systems, comprising: a graphite impregnated silicon carbide material.
 6. The bearing of claim 5, wherein the bearing is adapted for use in a downhole centrifugal pump.
 7. The bearing of claim 5, wherein the bearing is adapted for use in a downhole multistage pump.
 8. The bearing of claim 5, wherein the bearing is adapted for use in a downhole motor protector.
 9. The bearing of claim 5, wherein the bearing is a radial journal bearing.
 10. The bearing of claim 5, wherein the bearing is selected from thrust bearings, tilt pad bearings, lobed bearings, lemon bore bearings, and pressure dam bearings.
 11. A multiphase downhole pump, comprising: an electrical submersible pump having self-lubricating, abrasion resistant ceramic bearings.
 12. The multiphase downhole pump of claim 11, wherein the electrical submersible pump is a multistage pump.
 13. The multiphase downhole pump of claim 11, wherein the self-lubricating, abrasion resistant ceramic bearings comprise a graphite impregnated silicon carbide material.
 14. The multiphase downhole pump of claim 11, wherein the self-lubricating, abrasion resistant ceramic bearings are radial journal bearings.
 15. The multiphase downhole pump of claim 11, wherein the self-lubricating, abrasion resistant ceramic bearings selected from thrust bearings, tilt pad bearings, lobed bearings, lemon bore bearings, and pressure dam bearings.
 16. A downhole motor protector for use in a multiphase electrical submersible pumping system, comprising: self-lubricating, abrasion resistant ceramic bearings.
 17. The downhole motor protector of claim 16, wherein the self-lubricating, abrasion resistant ceramic bearings comprise a graphite impregnated silicon carbide material.
 18. The downhole motor protector of claim 16, wherein the self-lubricating, abrasion resistant ceramic bearings are radial journal bearings.
 19. The downhole motor protector of claim 16, wherein the self-lubricating, abrasion resistant ceramic bearings selected from thrust bearings, tilt pad bearings, lobed bearings, lemon bore bearings, and pressure dam bearings.
 20. A method of protecting bearings in a multiphase environment, comprising: providing self-lubricating, abrasion resistant ceramic bearings comprising graphite impregnated silicon carbide.
 21. A multiphase submersible pumping system, comprising: a submersible motor; a submersible pump powered by the motor; and a motor protector; wherein the bearings of the submersible pump and the motor protector are self-lubricating, abrasion resistant ceramic bearings.
 22. The multiphase submersible pumping system of claim 21, wherein the bearings are graphite impregnated silicon carbide bearings. 